Vacuum furnace



y 25, 5 H. E. MESCHER ETAL 3,185,460

VACUUM FURNACE Filed Aug. 15, 1963 3 Sheets-Sheet 1 INVENTORS 2 HAROLD E.MESCHER ROBERT L. ALLGEIER BY 430/15 M ATTORNEY y 1965 H. E. MESCHER ETAL 3,185,460

VACUUM FURNACE Filed Aug. 15, 1965 3 Sheets-Sheet 2 INVENTORS HAROLD E. MESCHER ROBERT L.ALLGE|ER BY W5. M

ATTORNEY y 25, 1965 H. E. MESCHER ETAL 3,185,460

VACUUM FURNACE 5 Sheets-Sheet 3 Filed Aug. 15, 1965 INVENTORS HAROLD E. MESCHER BY ROBERT L.ALLGEIER yak 5M ATTORNEY United States Patent 3,185,460 VACUUM FURNACE Harold Mes cher, Rivera, and Robert L. Allgeicr,

Valinda, Califl, assignors to Pacific Scientific Company, San Francisco, Calif., a corporation of California Filed Aug. 15, 1963, Ser. No. 302,250 4 Claims. (Cl. 263-40) This invention relates generally to vacuum furnaces,

and the invention has reference more particularly to a cold wall type vacuum furnace suitable for metallurgical uses such as sintering, heat treating, and brazing operations.

Cold wall vacuum furnaces as heretofore constructed generally used cylindrical radiation heat shields therewithin, arranged concentrically. and mutually spaced apart, said shields being of sheet metal of substantial thickness of the order of three-hundredths of an inch for the innermost shield and with the outer shield of provided with ribs which not only serve to stiffen the shields against bending, but also serve to mutually space the shields from one another, thereby preventing distortion of the shields in use and providing for long life of the same.

A feature of the present invention is to provide novel inner cylindrical shields of relatively thinmaterial such as tungsten, tantalum or molybdenum, the thickness of such cylinders being of the order of five-thousandths of an inch as compared with the relatively thick shields used heretofore, the thin shields enabling the overlapping ends thereof to be secured together by bending or crimping into a imple folded metal joint, thereby doing away with rivet-s which tend to cause cracking, the transverse joints of the shields being overlapped and held together by suitable tension members.

These and other features and advantages of the present invention will become more apparent after a perusal of the following specification taken in connection with the accompanying drawings wherein:

FIG. 1 is a plan view, partly in section, of a cold wall vacuum furnace illustrating the novel shield structure of this invention in use;

FIG. 2 is a vertical sectional view withparts broken away of the furnace of FIG. 1;

FIG. 3 is an enlarged fragmentary view the line 3 3 as shown in FIG. 1; and

FIG. 4 is a fragmentary view taken along the line 44 of FIG. 3 looking in the direction of the arrows.

Similar characters of reference are used in the above figures to designate corresponding parts.

Referring now to the figures of the drawings, the reference numeral 1, 1' designates the hollow outer wall casing of a cold wall furnace, which casing is shown as of cylindrical shape and is adapted to receive circulating cooling liquid, such as water, in the water jacket provided between the wall portions 1 and 1. As shown in FIG. 2, the cylindrical casing 1, 1 is flanged at its top and bottom and abuts similar flanges of cup or dome like top and bottom casing sections 2 and 3.

In use, the bottom casing section 3 is adapted to be taken along 3,185,460 Patented May 25, 1965 lowered away from the casing 1, 1 by means of a plunger 4 which is operated by a piston moving within a pneumatic cylinder (not shown) forthe purpose of loading and unloading the furnace. The movement of the bottom section 3 is controlled by rollers 19 carried by brackets attached to bottom section 3 and running on guides 20 supported from frame members 21. The furnace is adapted to be evacuated as by use of an oil or mercury diffusion pump coupled to furnace outlet 22. The furnace can be loaded by lowering the bottom section 3 away from stationary main casing 1, 1', whereupon the work can be placed uponthe hearth 5 that is supported by rods v6 upon the bottom section 3 and thereafter raised into the furnace proper. The work suchas 7 placed on hearth 15 is adapted to be heated by heating elements 8 fed from a multi-phaseline through water cooled feed members 9 and 9.

The work and the heating elements 8 are surrounded by the novel cylindrical radiation shields 10 of this in vention, these heatshields being arranged concentrically and mutually spaced apart as especially illustrated in FIGS. 1 and 3, the said shields being provided at regular intervals around the periphery thereof with V-shaped ribs 11 projecting outwardly therefrom which serve as stifieners and spacers, the outer end of each rib abutting the next concentric shield 10. The ribs 11, occurring at regular intervals around the peripheries of the shields, serve to greatly reinforce the relatively thin shields and prevent their distortion in the high heat of the furnace. The spacing provided by the ribs 11 thu enables the shields 10 to be made of relatively thin material; for example, material of the order of five-thousandths of an inch can be used compared with a much heavier material used heretofore. Since the metal of the ribs is thin, the joints in the cylindrical members can be made by simply crimping or folding the metal edges, as indicated at 12, so that they interlock with each other, thereby doing away with rivet which tend to fail and cause cracking at the joints due to heat expansion and contraction in use. Owing to the multiplicity of the V-shaped ribs, the series of cylindrical heat shields serve to reinforce each other and make a relatively rigid structure, as can be seen by viewing FIG. 1.

Ordinarily, owing to the height of the furnace, it is necessary to use two or more vertically disposed tiers of cylindrical shields, and heretofore such shields have been secured together as by riveted joints. In the present inoutermost one 15, which is simply a cylindrical shield,

has its upper and lower sections held together by means of the overlapping join-ts plus the tension of wire 13, which, in a typical furnace, may be of the order of twohundredths of an inch in diameter. The assembled concentric side cylindrical heat shields 10 andltl' are supported by radially extending support pins 23 projecting from the casing wall 1, these pins passing through suitable holes provided in the upper and lower heat shields 10 and 10'. The outermost heat shield 15, since it is in a relatively cool part of the furnace, can be a simple cylindrical shield with riveted or welded, or otherwise oined, vertical and horizontal or girth joints, and it is of course strengthened at regular intervals by the abutting V-shaped ribs 11 of the next adjacent heat shield 10 or 10 as the case may be.

The horizontal heat shields 16 and 16 at the upper and lower part of the furnace are also provided with V-shaped ribs 11 which serve to stiffen these plates and prevent their sagging in use. These plates are shown mounted on bolts or rods 18 at the top and rods 6 at the bottom of the furnace and may be additionally spaced apart by use of suitable spacers. The heat shields at the top and bottom of the furnace are relatively small as compared to the cylindrical shields 10, 10' at the sides of the furnace and so are not subject to the warping or distortion such as tends to occur in side shields.

With this novel construction of heat shields at the sides of the furnace, it is found that the life and eficiency of the heat shields in use is materially prolonged, thereby considerably reducing the down time of the furnace as Well as saving considerable expense in use. Further, since it is possible to use extremely thin sheets, they will cool rapidly when the furnace is turned off, thereby materially reducing the cycle time.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a cold wall furnace of the character described, a casing, and mutually spaced heat shields of very thin sheet metal within said casing, said heat shields being deformed at intervals to produce projecting continuous ribs for abutting adjacent similarly deformed shields, thereby determining the spacing of said heat shields, the said ribs serving to uniformly space said shields over their entire areas and to stiffen said shields and prevent injurious deflection thereof under the heat of the furnace.

2. A cold wall furnace providing a hearth therewithin for receiving work to be treated, heating elements surrounding the work within said furnace, mutually spaced extremely thin metal cylindrical heat shields positioned externally of said heating elements and within said furnace for retaining heat therewithin, said heat shields being formed with radially projecting mutually spaced V- shaped continuous ribs for stiffening said heat shields and also for determining the uniform spacing of said heat shields, said ribs abutting adjoining heat shields and serving to reinforce all of the heat shields of the furnace, and supporting members for supporting said heat shields within the furnace, the extremely thin heat shields enabling the furnace to cool rapidly with the heat off, thereby materially reducing the normal cycle time of the furnace.

3. A cold wall furnace as defined in claim 2 wherein said cylindrical heat shields are arranged in vertical overlapping pairs, and tie wires extending around said heat shields and passing through apertures in said overlapping V-shaped ribs for retaining the pairs in assembled relation.

4. A cold wall furnace as defined in claim 2 wherein each cylindrical heat shield is provided with a vertical folded joint enabling ready expansion and contraction of the shield in use without tendency to crack at the joint.

References Cited by the Examiner UNITED STATES PATENTS 2,476,916 7/49 Rose et a1. 26350 3,033,547 5/62 Baker et a1 263-40 FOREIGN PATENTS 759,777 10/56 Great Britain.

CHARLES SUKALO, Primary Examiner.

JOHN J. CAMBY, Examiner. 

1. IN A COLD WALL FURNACE OF THE CHARACTER DESCRIBED, A CASING, AND MUTUALLY SPACED HEAT SHIELDS OF VERY THIN SHEET METAL WITHIN SAID CASING, SAID HEAT SHIELDS BEING DEFORMED AT INTERVALS TO PRODUCE PROJECTING CONTINUOUS RIBS FOR ABUTTING ADJACENT SIMILARLY DEFORMED SHIELDS, THEREBY DETERMINING THE SPACING OF SAID HEAT SHIELDS, THE SAID RIBS SERVING TO UNIFORMLY SPACE SAID SHIELDS OVER 